Historically, iron sights have been mounted to barrels, so as to provide a means for aiming the firearm. Iron sights continue to be a reliable, light-weight, and low cost method. More recently, however, optical sights and mounts have become more common in the industry, with most after-market scopes being mounted to receivers because the scope is held closer to the eye, and, typically, there is no need for the additional complexity or weight of a cantilever. Forward mounted (long eye-relief) scopes are also available, such as unity power red dot scopes, and are particularly suited for some fixed-barrel rifle applications.
However, take-down or break-down rifles, such as certain models of the Ruger 10/22 or others, typically exhibit more tolerance stack-up and/or relative movement between the receiver and the barrel than do fixed barrel rifles, due to the take-down feature itself, thus requiring more time and effort to properly sight in and/or exhibiting changes over time (for example, due to variations in temperature, components loosening after use, etc.). In some cases, after market barrels may be attached, or existing barrels may be modified by a gunsmith so as to provide a fastening feature in the barrel itself, to which a scope mount may be attached.
Similarly, some systems, such as the Steyr AUG, have what are commonly referred to as “quick change” barrels. These systems readily reconfigurable with different length barrels, so as to function as a light support weapon, rifle, carbine, or submachinegun, and different calibers (with other associated parts swapped). These are really takedown rifles even though they are not typically recognized as such, and may have some challenges similar to those previously described above.
Although these arrangements are generally functional, there remains a need for a reliable and accurate no-gunsmithing means for attaching an after-market accessory or scope to a barrel for a take-down rifle or other weapons.